A surgical instrument for surgically joining tissue includes a handle assembly, an elongate member extending distally from the handle assembly, an end effector disposed adjacent a distal portion of the elongate member, and an actuation assembly operatively associated with the handle assembly. The actuation mechanism includes a thrust bar disposed at least partially within the elongate member and a distal slide member. The thrust bar has a proximal portion, a distal portion, a first lateral side and a second lateral side and is configured to move between proximal and distal positions with respect to the handle assembly. The distal slide member is positioned adjacent the first lateral side of the thrust bar and is adjacent the distal portion of the thrust bar. The proximal portion of the distal slide member is adapted to slide relative to the thrust bar when thrust bar moves in a curvilinear direction.